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ceremcem/bootable-backup-changes.md

Last active October 13, 2017 22:55
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bootable-backup-changes.md

1. Prepare yourself

Everything may go wrong in this process. Make backups, prepare a live distribution that can connect to internet.

2. Prepare a new rootfs

Sync your current root filesystem to another location, eg. /NEW_ROOTFS

  1. Edit /NEW_ROOTFS/etc/fstab to mount proper devices
  2. Edit your rootfs synchronization tool (smith-sync, btrbk, dcs-tools, snapper, ...) config to backup between correct devices
  3. Edit /NEW_ROOTFS/etc/crypttab to reflect correct keys/entries
  4. Set NOCOW (chattr +C folder) attributes of folders if there were any (like Chromium's ~/.config/chromium, VM disk images, etc)

3. Prepare initrd

initrd.img is responsible for mounting the correct rootfs. Thus, new GRUB entry (or the bootloader entry you use now) should pass the NEW_ROOTFS strategy/devices to the initrd.

For example, a rootfs may be on a btrfs subvolume on a btrfs filesystem on a LVM volume on a LUKS partition. Now new entry should know about

  • New btrfs subvolume (if it is changed)
  • New LVM volume names (it is probably changed)
  • New LUKS partition UUID (it is absolutely changed)

This is a "new device" scenario where the strategy (btrfs_subvolume/btrfs/LVM/LUKS) is unchanged.

You may want to change the strategy, for example XFS/LUKS/RAID. If this is the case, initrd should also know about the correct mount order.

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